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4200 - Formal Languages: Final Exam Fall 2019
发布时间:2022-12-06
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4200 - Formal Languages: Final Exam
Fall 2019
Problem 1
10 points
Alphabet Σ = {0, 1}.
A = {0, 1}*
B = L(α)
where α is a regular expression: α = 0* n 1*
C = A u B
For each of the languages (A, B , B , and C), write down five example strings in it. Construct a deterministic finite automaton (DFA) that recognizes the language C .
Problem 2
10 points
Define a nondeterministic finite automaton (NFA) M such that L(M) = L(β) where β is a regular expression:
β = (1 > e)* > 11* e(0 > 1) > e
Note: for grading purposes, please do NOT simplify the given regular expression before constructing the NFA.
Problem 3
10 points
Write down a context-free grammar for the following language D . Please use S as the start variable. D = { 1北+2y0北 1y l 北, y ● 0 }
Problem 4
20 points
Is there a decidable Turing machine that accepts the following language D? (i.e. a Turing machine that halts for every input).
D = { 1北+2y0北 1y l x, y ● 0 }
· If yes, please describe in English how this Turing machine works (as if you were trying to convince a friend that this algorithm works). In addition to the English description, transition diagrams are optional (if you think it helps explaining), but not required.
· If no, please explain why.
Problem 5
10 points
Is the language D in Problem 4 regular or not?
D = { 1北+2y0北 1y l x, y ● 0 }
If yes, please show that via a DFA/NFA or a regular expression. If not, please prove it via pumping lemma for regular languages.
Problem 6
10 points
E = { 1北+2y0北 1y 1y l x, y ● 0 }
Please answer Yes or No.
· Is the language E regular?
· Is the language E context-free?
· Is the language E Turing-decidable?
· Is the language E Turing-recognizable?
Problem 7
15 points
G = { 1北+2y0北 1y 0y l x, y ● 0 }
Please answer Yes or No.
· Is the language G regular?
· Is the language G context-free?
· Is the language G Turing-decidable?
· Is the language G Turing-recognizable?
If you think the language G is not context-free, please prove it via pumping lemma for context-free languages.